All:
One thing to note.. when you can do an implied connection setup, the
3-way hand shake has the potential to carry data (don't know if tcp
does in FreeBSD)
on the third leg of the 3-way handshake.
This is one of the reasons SCTP uses this.. since we often will
carry data an the third and even possibly the 4th leg of the handshake
(we
have one extra leg).
Taking this feature out of TCP will make it so we will be like all other
o/s's and the socket semantic will prevent you from doing data on the
third leg..
----SYN---->
<----SYN-ACK---
----ACK--->
instead of
----SYN-->
<---SYN-ACk--
---ACK+DATA-->
In the past I have mentioned in classes I teach that TCP is capable of
this but the O/S's
of the world do not allow this later behavior..
Just thoughts and ramblings ;-)
R
On Sep 10, 2010, at 2:51 PM, Karim Fodil-Lemelin wrote:
On 31/08/2010 5:32 PM, Robert Watson wrote:
On Tue, 31 Aug 2010, Andre Oppermann wrote:
I'm not entirely comfortable with this change, and would like a
chance to cogitate on it a bit more. While I'm not aware of any
applications depending on the semantic for TCP, I know that we do
use it for UNIX domain sockets.
I don't have any plans to remove the implied connect support from
the socket layer or other protocols, only from TCP.
Right -- the implicit question is: why should TCP be the only
stream protocol in our stack *not* to support implied connection,
when we plan to continue to support it for all other protocols?
For deprecating this part of the TCP API there is no documentation
to the implied connect in tcp(4). In sendto(2) it doesn't
differentiate between protocols and simply says: "... sendto() and
sendmsg() may be used at any time." For MSG_EOF it says that is
only supported for SOCK_STREAM sockets in the PF_INET protocol
family. These sentences have to be corrected.
In general, deprecating is taken to mean providing significant and
explicit advance warning of removal -- for example, updating the
8.x man page to point out that the feature is deprecated and it
will not appear in future releases of FreeBSD.
Robert
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Hi,
For what its worth, we at Xiphos (now XipLink), are still using
sendto and T/TCP and is one of the reasons we've chosen FreeBSD more
then 10 years ago!
Best regards,
Karim.
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------------------------------
Randall Stewart
803-317-4952 (cell)
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